Sudden cardiac arrest is the leading cause of death in the United States and Canada and accounts for one in every six deaths. The Centers for Disease Control and Prevention estimate that approximately 405,000 people annually in the United States die from coronary heart disease. About 250,000 of these deaths occur outside of a hospital setting. Achieving high survival rates depends upon a public that is well trained in Cardiopulmonary Resuscitation (“CPR”) because arrival of emergency medical services typically takes longer than five minutes, but irreversible brain damage predictably develops after only four minutes of cardiac arrest.
CPR is a procedure performed on a patient undergoing cardiac arrest. CPR includes compression of the patient's chest by a rescuer (alternatively “resuscitator”) and can be performed with or without ventilating the patient. The chest compressions are performed to create artificial blood flow in a patient. The rescuer repeatedly compresses the patient's chest in order to manually pump blood through the patient's heart so that blood continues to circulate to the patient's vital organs. These compressions should occur at a rate of 100 or more compressions per minute. Providing fewer than 100 compressions per minute decreases effectiveness of CPR. A problem arises when the lay public does not know or does not recall the desired rate of compressions. What is more, even if the rescuer knows the desired rate, it is difficult to maintain a consistent compression rate without assistance. Further, CPR without ventilation is less effective than CPR with ventilation because oxygen saturation falls. This drop in oxygen decreases patient survival after four to six minutes of compression-only CPR.
Mouth-To-Mouth Ventilation (“MTMV”) CPR is the current standard for treating out-of-hospital cardiac arrest. During MTMV CPR, the rescuer performs chest compressions for a period of time, and then stops the compressions and attempts to ventilate the patient. During ventilation, the rescuer tilts the patient's head back, lifts the chin, pinches the patient's nose, creates an air seal between the patient's mouth and the rescuer's mouth, and provides two rescue breaths by exhaling into the patient's mouth. Typically, the ratio is thirty compressions to two breaths. MTMV CPR has several limitations including: (1) rescuer fear of disease transference from the patient; (2) interruption of chest compressions in order to ventilate the patient; (3) inadequate volumes of gas exhaled by the rescuer into the patient's lungs; and (4) ineffective ventilation due to utilization of the rescuer's expired gasses which are only about 15% oxygen.
MTMV CPR remains the current standard in airway management utilized by the lay public; however, the lay public has demonstrated consistent difficulty and hesitation in performing standard MTMV CPR. Studies illustrate that MTMV CPR is often performed incorrectly, resulting in inadequate ventilation. For example, missing or poorly performing any ventilation steps results in ineffective ventilation. Because of this, patients have better outcomes when bystanders perform CPR without attempting to ventilate the patient. Moreover, ventilation effectiveness is inherently limited by utilizing the rescuer's expired gases because the fraction of inspired oxygen (“FiO2”) is only about 15%. Further, even if the rescuer properly performs each step in MTMV CPR, blood flow in the patient is hindered because the rescuer must interrupt the process of chest compressions.
Alternatives to MTMV CPR include CPR using Bag-Valve-Mask ventilation, endotracheal intubation, and Laryngeal Mask Airway ventilation. These devices are not typically available to the lay public when performing CPR and some can even endanger the patient if used incorrectly, e.g., by the lay public. A bag-valve-mask uses a mask to create the air seal over the patient's mouth and nose. A bag is then compressed by hand in order to force atmospheric air, which is 21% oxygen, into the patient's lungs. Pressure-sensitive valves on the bag-valve-mask control the direction of airflow. Use of the bag-valve-mask still hinders blood flow in the patient because the rescuer must interrupt chest compressions in order to ventilate the patient.
Endotracheal intubation involves inserting a tube through the patient's mouth and into the trachea. The patient is ventilated by a bag-valve placed on the exposed end of the tube or the rescuer exhaling into the exposed end. Endotracheal intubation is an advanced procedure that involves slow insertion times and has been shown to have a failure rate in excess of 30%. Further, use of endotracheal intubation still hinders blood flow in the patient because the rescuer must interrupt chest compressions in order to ventilate the patient.
Laryngeal Mask Airway (“LMA”) ventilation involves inserting a device such as an I-GEL® suppraglottic airway device with a soft, gel-like, non-inflatable cuff (Intersurgical Ltd., Wokingham, Berkshire, UK) into the patient's mouth for positive pressure ventilation. The I-GEL® suppraglottic airway device is positioned in the supraglottic airway of the patient to deliver air to the patient's lungs. The patient is ventilated by a bag-valve placed on the exposed end of the I-GEL® suppraglottic airway device or by the rescuer exhaling into the exposed end. Use of the I-GEL® suppraglottic airway device still hinders blood flow in the patient because the rescuer must interrupt chest compressions in order to ventilate the patient.
In the case of out-of-hospital cardiac arrest, the current survival rate is 7.6%. As a result, the AMERICAN HEART ASSOCIATION® (American Heart Association, Inc., Dallas, Tex.) (“AHA”) has called for research regarding alternative methods of CPR. Thus, it would be desirable to develop a system that overcomes the problems and limitations associated with traditional methods of CPR to increase rates of survival for patients suffering from cardiac arrest.